SimB: Difference between revisions

SimB

SimB is a simulator built on top of ProB. It is available in the latest SNAPSHOT version in the new JavaFX based user interface ProB2-UI, The modeler can write SimB annotations for a formal model to simulate it. Furthermore, it is then possible to validate probabilistic and timing properties with statistical validation techniques such as hypothesis testing and estimation.

Using SimB

Start SimB via "Open Simulator" in the "Advanced" Menu after opening a machine.

Now, you can open a SimB file (JSON format) controlling the underlying formal model.

A SimB file consists of probabilistic and timing elements to simulate the model. Within these elements, the modeler can user B expressions which are evaluated on the current state.

In the following, an example for a SimB file controlling a Traffic Lights for cars and pedestrians is shown:

{
 "activations": [
  {"id":"$initialise_machine", "execute":"$initialise_machine", "activating":"choose"},
  {"id":"choose", "chooseActivation":{"cars_ry": "0.8", "peds_g": "0.2"}},
  {"id":"cars_ry", "execute":"cars_ry", "after":5000, "activating":"cars_g"},
  {"id":"cars_g", "execute":"cars_g", "after":500, "activating":"cars_y"},
  {"id":"cars_y", "execute":"cars_y", "after":5000, "activating":"cars_r"},
  {"id":"cars_r", "execute":"cars_r", "after":500, "activating":"choose"},
  {"id":"peds_g", "execute":"peds_g", "after":5000, "activating":"peds_r"},
  {"id":"peds_r", "execute":"peds_r", "after":5000, "activating":"choose"}
 ]
}

Probabilistic and Timing Elements in SimB

The SimB file always contains an activations field storing all elements controlling the simulation in a list. There are two types of activations: direct activation and probabilistic choice. All activations are identified by their id.

Direct Activation

{
   "id":  ...
   "execute": ...
   "after": ...
   "activating": ...
   "activationKind": ...
   "additionalGuards": ...
   "fixedVariables": ....
   "probabilisticVariables": ....
   "priority": ...
}

Probabilistic Choice

Real-Time Simulation

Timed Trace Replay

Monte Carlo Simulation

Hypothesis Testing

Estimation